I have observed guys will often address as 'buddy' another guy either younger, smaller, or somehow bearing less status; this far it is not an overt, hostile put-down, but a more subtle; the speaker extends his friendship even while asserting superiority, whether in age, status or knowing experience.

I would say this sphere of the word only extends especially to acquaintances rather than the closest of friends; among close friends, if there's an alpha in the group, he might use 'buddy' on the others; but if there's a perceived equality, 'buddy' may then not carry these subtle social shades.